Zeolites, both mineral and synthetic, have been used in a variety of catalytic and adsorptive operations. Most zeolitic materials are porous ordered aluminosilicates having a definite (although often undetermined) crystal structure. The structure may have a number of small cavities interconnected by a number of larger channels. These cavities and channels are uniform in size within the particular zeolitic material. The above-mentioned catalytic and adsorptive processes make use of these cavities and channels since by proper choice of zeolite, the zeolite channels will reject some molecules, because of their size and/or affinity, and accept others.
These zeolites typically are describable as a rigid three-dimensional framework of silica and alumina (or other tetrahedral ions) wherein the silica and alumina (T atoms) tetrahedra are linked through common oxygens. The charge balance of the zeolite may be satisfied by inclusion of a proton, metal or ammonium cation. The catalytic and adsorption properties of the zeolite may be varied by changing the ions within the zeolite, or by changing the nature and ratios of the T atoms. Conventional ion exchange techniques may be used to change these cations. Details of nomenclature in these systems, as recommended by IUPAC, has been outlined by Barrer (Pure and Appl. Chem., 51, 1091 (1979)), and a recent review by J. V. Smith (Chem. Rev. 88. p. 149-182 (1988)).
There are a large number of both material and synthetic zeolitic structures. The wide breadth of such numbers may be understood by considering the work "Atlas of Zeolite Structure Types" by W. M. Meier and D. H. Olson (2nd edn., Butterworths/Intl. Zeolite Assoc. (1988)).
It is known to substitute such elements as gallium and germanium into some zeolite structures in the place of at least a part of the framework aluminum. More recently a wide variety of such element substitutions have been reported, particularly for the near silicas such as ZSM-5. However, in the high Al content zeolites, such substitution is usually very specific, allowing some T atom replacement only with specific elements within specific ranges. Such replacements seem to be controlled by the "flexibility" of the particular framework type, allowing only limited variation in T-O bond lengths and T-O-T angles. In some cases metallosilicates are possible which do not allow substitution of Al into T atom positions, or allow such substitution in a very limited manner--ECR-9 seems to be such a material.
The inventive zeolite ECR-9 is a gallium silicate zeolite, a sample of which was indexed on an orthorhombic lattice having the approximate parameters: a=14.2 .ANG., b=16.2 .ANG. and c=8.6 .ANG. in the Si-Ga form. The composition has the general composition, in terms of oxides, of: EQU 0.9 to 1.3 K.sub.2 O:Ga.sub.2 O.sub.3 :3 to 8 SiO.sub.2 :0 to 6 H.sub.2 O
up to 40% of the gallium can be substituted by transition metals, such as Fe, Cr, Ni, Co, Zn, B, etc. Only low levels of Al substitution are tolerated (less than 10%). K may be partly substituted by Na and TEA (tetraethyl ammonium). Depending upon the nature and degree of such substitutions, unit cell values may vary around the value given above, and may even cause distortion of the orthorhombic symmetry observed for the Si-Ga form.
As mentioned above, other gallium-containing zeolites are known, and several of these have been described in the literature (Newsam and Vaughan, Proc. 7th Intl. Zeolite Conf., SSSC #34, Kodansha/Elsevier, p. 457 (1986)). However, gallium substitution may cause major disruption of structures, and induce such metastability that some known zeolites may not accept Ga substitution, resulting instead in either new zeolites or amorphous products.
For instance, U.S. Pat. No. 3,431,219, to Argauer, issued Mar. 4, 1969, discloses a crystalline gallium silicate of the compositions, in terms of oxide mole ratios: EQU 0.9.+-.0.2Na.sub.2 0:0.1 to 1 Ga.sub.2 O.sub.3 :0 to 0.9 Al.sub.2 O.sub.3 :3 to 6 SiO.sub.2 :3 to 12 H.sub.2 O
The zeolite has the crystalline structure of the large pore zeolite Type X, which is isostructural with naturally occurring faujasite. Other gallium faujasites of the X and Y types have been reported by Vaughan et al (Amer. Chem. Soc. Symp. Ser. 218, p. 231 (1983)).
Similarly, U.S. Pat. No. 4,083,807 to McKinney et al, issued Apr. 11, 1978, discloses zeolites which may contain some gallium in the framework position.
U.S. Pat. No. 4,331,774 to Boersma, issued May 25, 1982, details a gallium silicate which is stable to about 600.degree. C.; has very strong peaks on the X-ray powder diffraction pattern at Bragg angles of 23.1 to 23.4 and 23.8 to 24.1 (20) strong peaks at 7.8 to 8.2 and 24.2 to 24.8 (20) and medium peaks at 8.7 to 9.1 and 29.7 to 30.1 (20); and, wherein the Ga.sub.2 O.sub.3 /SiO.sub.2 molar ratio is less than 0.1.
None of the prior art teaching describes a zeolite having the structure and composition of ECR-9, having the X-ray diffraction pattern indigeneous to ECR-9, the essential lines of which are shown in Table 1, additionally recognizing that changes in cation content and T atom composition may influence the intensity of these diffraction peaks.